Electrochemical Capacitors : Challenges and Opportunities for Real - World Applications

53 People today are very familiar with different battery technologies, from small zinc-air button cells to AAA alkali cells to spiral wound lithiumion laptop batteries to fifty-pound lead acid batteries found in automobiles. This situation has come about because people rely heavily on battery power.1 Common battery applications include, for instance, power for cell phones, Sony Walkman, PDAs, laptop computers, Ipod players, digital cameras, and on and on. In sharp contrast, people today are much less familiar with capacitor technologies, although capacitors also store energy. One reason for this is that capacitors have exceptionally long life and seldom need service while batteries, bar none, eventually need charging or replacement. The aim of this article is to express in a clear fashion the differences between battery and capacitor technologies, identify several applications that exploit one or more characteristics unique to electrochemical capacitor energy storage, and finally point out some key technology challenges for their further development and greater market acceptance.